Diablo 1 and Heroes of might and Magic 3 has only not been installed on my computer after upgrades of the operating system or when I bought a new computer.
The digital games installed on switch that I will never delete is New Pokémon Snap and all the Ace attorney Collections. The rest of the games I value as high or higher I have a physical copy of. Sure many need installation still but it does not take that long.
On PS5 I will never remove Hogwarts Legacy since it is my wife's favorite. I will keep the installation of Resident Evil 4 Remake as well, can't bother with installtion when I get the itch to save Ashley and upgrade weapons at the merchant.
When it comes to older systems I have a few games I never take out of my dedicated carrying bag for my DS. Fire emblem, Elite beat agents and Advance Wars dual Strike and Fire Emblem never leaves the GBA slot.